Module 15.12 Air Systems

Question 1

What would the internal temperatures be if there was only an ideal air/fuel ratio of 15:1?

Answer 1

2200 °C

Question 2

What temperature does the large volume of air cool the hot sections of the engine to?

Answer 2

800 to 1150 °C

Question 3

What is the most critical lubricating point in a gas turbine engine?

Answer 3

The exhaust turbine bearing.

Question 4

What two ways are exhaust turbine bearings cooled?

Answer 4

Air cooling and oil cooling.

Question 5

Where are cooling air inlets located?

Answer 5

Around the exterior of the engine.

Question 6

Why are cooling air inlets needed?

Answer 6

To cool the turbine case, bearings and nozzle.

Question 7

How is the engine exterior and nacelle cooled?

Answer 7

By passing fan air around them.

Question 8

How do the engine zones isolated from each other?

Answer 8

Fireproof bulkhead or seals

Question 9

What is zone 1?

Answer 9

Fan case compartment.

Question 10

What is zone 3?

Answer 10

Core engine compartment

Question 11

What is zone 2?

Answer 11

Intermediate compressor case compartment

Question 12

How is zone 2 cooled?

Answer 12

By fan air from the upper part of the fan duct.

Question 13

How are anti-icing systems controlled in flight?

Answer 13

By a switch on the flight deck.

Question 14

How does air exit after heating the lip?

Answer 14

A grill on the nose cowl.

Question 15

What is the temperature at the rear stages of the compressor?

Answer 15

350 °C to 400 °C

Question 16

How is the compressor rotor cavity cooled?

Answer 16

Air from the intermediate compressor stage

Question 17

What percentage of the primary airflow is directed inside the combustion liner?

Answer 17

20% - 30%

Question 18

What percentage of the secondary airflow is directed around the combustors periphery?

Answer 18

70% - 80%

Question 19

How does the secondary airflow provide cooling for the combustion liner?

Answer 19

It forms a cooling air blanket on both sides of the liner and centres the combustion flames so they do not contact the line.

Question 20

How is the turbine disc cooled?

Answer 20

Using engine bleed air.

Question 21

How are turbine Nozzle Guide Vanes (NGV) and turbine blades cooled?

Answer 21

Compressor air

Question 22

How are accessory’s cooled?

Answer 22

Air ducted from cowling intakes or from a specific stage of the compressor.

Question 23

What is used to seal engine bearing chambers?

Answer 23

Low pressure compressor bleed air.

Question 24

What is pressurised air used to do when it comes to bearing chambers?

Answer 24

It acts on the air seals and oil seals and has an additional sealing effect that prevents oil from escaping.

Question 25

How is air that enters the bearing compartments vented overboard?

Answer 25

Through the hollow N1 rotor shaft.

Question 26

What does the external air system do?

Answer 26

Cools and ventilates the external areas between the cowlings and the engine cases.

Question 27

When is the core compartment ventilated?

Answer 27

Only when the engine operates.

Question 28

What is a bowed rotor?

Answer 28

When the engine bends due to different expansions between the upper and lower engine zones.

Question 29

How is zone 1 cooled?

Answer 29

RAM air is used.

Question 30

Where is zone 2 fan air exhausted?

Answer 30

At the lower end, back into the air stream.